A system for the creation of national high resolution 3D radar mosaic has been developed and running in real-time at the National Severe Storms Laboratory of NOAA since June 2004. The national 3D mosaic ingests and quality controls base level reflectivity data from ~140 WSR-88D radars in the CONUS domain, and then objectively analyzes the data onto a seamless Cartesian grid (Zhang et al. 2004). The CONUS analysis domain is divided into 14 computation tiles. For each tile, volume scan data from individual radars are remapped onto the tile's 3-D Cartesian grid. The remapped fields from all the radars are mosaiced to produce a unified 3D grid for the tile. If single radar straddles more than one tile, and the volume scans data are processed multiple times, one for each tile. This procedure is not computationally efficient as most of the radars straddle one or more tiles. To address this issue, a new adaptive radar mosaic system was developed to improve the computational efficiency of the national 3D mosaic. Within the new system, data from individual radars are remapped onto a 3-D Single Radar Cartesian (SRC) grid. Each SRC grid is centered at a CONUS grid cell closest to the radar site and has the same spatial resolution and vertical levels as the 3D CONUS mosaic grid. . As a result, the SRC grids are fully aligned with the 3D CONUS grid (i.e., each SRC grid cell is overlapped with a CONUS grid cell). When mosaicing multiple SRC grids, a simple distance weighted mean is applied at each grid cell with multiple radar coverage. With the new system, each radar volume scan is only processed once in the SRC grid. Thus the computational efficiency is greatly improved allowing more frequent updates. The SRC grid also allows flexibility in spatial resolution and integration of data from different type of radars. Detailed description of the system will be presented at the conference.